Afterburner and muffler device



Oct. 5, 1965 w. MORRIS ETAL 3,209,532

AFTERBURNER AND MUFFLER DEVICE Filed April 1, 1963 3 Sheets-Sheet 1 E 52 as [#22455 W Maze/s COHN EHYMOND DZYATE Zoe/v5 Z. F QRZ/ER INVENTORS.

BY M:

Oct. 5, 1965 w. MORRIS ETAL 3,209,532

AFTERBURNER AND MUFFLER DEVICE a $5 Y r m y OL N 0 1 M W w w J .5m 4 6 WM m L o. m SWL m 5 W Y HNW B Cw J Filed April 1, 1963 Oct. 5, 1965 c. w. MORRIS ETAL AFTER BURNER AND MUFFLER DEVICE a E m mm mm m w mm N w I g w m m E g 5 8 m wF m 5 8T m Al m n: Q a WL N L E 2 M W \N 6 H 0 m2 wl Filed April 1, 1965 United States Patent 3,209,532 AFTERBURNER AND MUFFLER DEVICE Charles W. Morris, 11769 'Chenault St., Los Angeles,

John R. Ulyate, Torrance, and Lorne 'L. Frazier,

Gardena, Califi; said Ulyate and said Frazier assignors to said Morris Filed Apr. 1, 1963, Ser. No. 269,486 6 Claims. (Cl. 6030) This is a continuation-in-part of our copending application Serial No. 195,789 filed May 18, 1962, for Adaptable Afterburner.

The present invention relates in general to an afterburner and mufller device for reducing the content of hydrocarbons, carbon monoxide, oxides of nitrogen and other noxious components in exhaust gases from internal combustion engines. More particularly, the present invention pertains to a compact, light weight, inexpensive device which is free from numerous adjustable parts, is readily installed and easily adaptable for a wide variety of internal combustion engines, is capable of operating efiiciently over a wide range of engine operating conditions, rapidly obtains the temperature required to eliminate those compounds generally considered to be the primary cause of air contamination such as smog and is effective in dispersing pressure pulses in the exhaust gas flow to attenuate the pressure pulses and mufile the sounds of combustion.

Studies have established that the contamination of the atmosphere in and around metropolitan centers is primarily clue to the presence of hydrocarbon gases. It has also been established that the major contributing cause to such atmospheric pollution is the tremendous volume of hydrocarbon gases, carbon monoxide and nitrogen oxide discharged into the atmosphere from the exhaust and crankcases of automobiles and other vehicles driven by internal combustion engines. During idling and deceleration the exhaust gases carry very large quantities of hydrocarbons and carbon monoxide; during acceleration and at ordinary cruising speeds the hydrocarbon content of the exhaust gases is at excessive but there is a substantial concentration of nitrogen oxide gases in such exhaust gases. In metropolitan areas the progress of an automotive vehicle is a succession of idling interspersed with bursts of acceleration and periods of rapid deceleration; as a result, extremely large quantities of hydrocarbon gases, carbon monoxide and nitrogen oxides are discharged into the atmosphere. Research has shown that during deceleration as high as of the fuel is actually pumped out of the exhaust system in an unburned condition.

However, the flexibility of an internal combustion engine introduces a great number of very difiicult problems in the treatment of its exhaust gases. The operating conditions of an internal combustion engine may be classified as idling, deceleration, acceleration and cruising speeds. The hydrocarbon content of the exhaust gases varies greatly under these different operating conditions as does carbon monoxide and the nitrogen oxides. For example, during idling and deceleration the hydrocarbon content of the exhaust gases is high whereas during acceleration and cruising it is relatively low. An average internal combustion engine of the character used in an automobile may carry 800 ppm. of hydrocarbons in its exhaust during idling. This may drop to 200 ppm. during acceleration and cruising, but during deceleration the hydrocarbon content of the gases being exhausted may readily reach 5500 ppm.

Similarly, the carbon monoxide content of exhaust gases may vary from 6% during idling, to 2' /2% during acceleration, to 0.5% during cruising and rise to 4% during deceleration. In addition, temperatures above 1200 F. are required to cause combustion of carbon monoxide and temperatures above 1500" to 2000 F. are necessary in order to obtain complete combustion of carbon monoxide. The exhaust temperature (at the outlet of an exhaust manifold of an internal combustion engine) may vary from 400 F. to 500 F. during deceleration and be about 400 F. during idling. During cruising speeds the temperatures reach 800900 F. and during acceleration reach 1100 F.1200 F. It can easily be seen that during normal operation, the engine temperature is not suificiently high to actually burn or cause combustion of carbon monoxide.

Another variable which must be taken into consideration comprises the volumetric flow of exhaust gases; the volumetric flow is ordinarily low during idling and deceleration, e.g., 5l0 cubic feet per minute, but it is high during acceleration and cruising, e.g., greater than cubic feet per minute.- Moreover, the pressure of the exhaust gases also varies within wide limits. The pressure of the exhaust gases is ordinarily low during idling and deceleration but is high during acceleration and cruising.

In addition to the effect on exhaust gases, the widely Varying operating conditions have a major etfect on the vent gases from the crankcase. At all times during the operation of an internal combustion engine, a significant amount of evaporation takes place from the hot oil in the crankcase and these vapors are usually discharged to the atmosphere through the oil-filling aperture. However, during cruising and particularly during acceleration, the quantity of vent gases from the crankcase is greatly increased because combustion gases from the cylinders blow by the pistons into the crankcase. In fact, the quantity of crankcase vent gases in total is so great that it has been estimated that it contributes 10% to 40% of noxious gases discharged by vehicles, such as hydrocarbons and carbon monoxide.

Finally, it should be noted that there is a substantial proportion of nitrogen oxide in the exhaust gases, particularly during acceleration and cruising. It has been found that if the proportion of exhaust gases containing such nitrogen oxide is cooled to preferably atmospheric temperature or at least below F. and then recycled into the intake manifold of the engine, a substantial reduction of the 'total content of these components conventionally discharged to the muflier or the atmosphere is effected.

The invention of our prior copending application Serial No. 195,789 filed May 18, 1962, directed toward solving the aforementioned problems, comprised in general the provision of an enclosed burner chamber having an ignition means mounted therein and an outlet remote from the ignition means. A bank of small venturi pumps Was associated with the burner chamber to admix additional gases comprising air to a portion of the exhaust gases directed into the burner chamber. The bank of venturi pumps comprised generally a fixed orifice means for providing a plurality of spaced axially parallel pump inlet sections opening to the exhaust gases, a pump throat section axially aligned with each inlet section and mounted in a Wall means spaced from said fixed orifice means, means on each throat section providing at least one port therein opening outwardly of said burner chamber between said fixed orifice means and said wall means, and a diffuser section associated with each throat section opening into the burner chamber. Means were provided for supplying gas comprising air between the fixed orifice means and the indicated wall means. The added gas comprising air was thus entrained into the individual venturi pumps through the ports in the throat sections thereof.

Valve means were also provided responsive to operating conditions of the internal combustion engine for bypassing a portion of the exhaust gases past the bank of venturi pumps. By selectively directing the fiow of exhaust gases past the bank of venturi pumps when the rate of flow of exhaust gases is increased, the amount of air added to the total volume of exhaust gases can be held substantially unchanged when the flow rate of exhaust gases is increased to more than twice its minimum rate.

We have found that when starting an internal combustion engine in a cold condition, the exhaust gases must warm the exhaust manifold of the engine, the exhaust pipe and the internal parts of the adaptable afterburner before it is possible to obtain more than spasmodic combustion in the combustion chamber, particularly during deceleration of the engine. Also, the prior bypassing of the exhaust gases past the bank of primary venturi pumps and then almost immediately emitting it to the atmosphere has caused objectionable sounds of internal combustion to be emitted from the adaptable afterburner.

It is therefore an object of our present invention to disclose and provide both apparatus and methods for modifying the exhaust gas from an internal combustion engine to complete the combustion therein which is capable of fast warm-up, attains stabilized burning within the burner chamber more quickly than heretofore possible such that combustion within the burner chamber is sustained during deceleration of the internal combustion engine in a shorter period after starting the engine and in which the sounds of internal combustion are effectively mufiied or silenced within the device prior to the emission of exhaust gases to atmosphere.

It is another object of the present invention to disclose and provide a compact inexpensive combination afterburner and muffler device which may be readily attached not only to new internal combustion engines and vehicles employing the same, but which can also be adapted readily and be attached to existing vehicles by merely replacing existing mufilers therein.

Another object of the present invention is to disclose and provide a combination afterburner and mufiier device which does not employ catalysts and in which the operative temperatures for sustained combustion within the device are more rapidly reached so that the major portion of hydrocarbons and carbon monoxide contained in the exhaust gases upon starting of the internal combustion engine may be promptly consumed and burned and continuously thereafter even during short periods of operation.

A further object of the present invention is to disclose and provide an afterburner and mufiier device capable of burning exhaust gases with air added in approximate accordance with the variation in the combustible content of said gases under different operating conditions of the engine and which is further capable of mufiiing all exhaust gases emitted from the internal combustion engine, the operation thereof being accomplished automatically and without the use of complicated or expensive machinery or instrumentation.

A still further object of the present invention is to disclose and provide apparatus and methods for directing pressure pulses of exhaust gases emitted by an internal combustion engine in predetermined flow paths for introducing an additive gas comprising air to a portion of said pulses and mixing it therewith while dividing all of said pulses into a plurality of elements, and thereafter attenuating said elements and thereby muflling the sounds of internal combustion emitted with said exhaust gases from the internal combustion engine.

Generally stated, the afterburner and mulfier device for use in modifying exhaust gases from an internal combustion engine, in accordance with the present invention, comprises a housing to be associated with an exhaust pipe of an internal combustion engine replacing the conventional mufiier. An enclosed burner and mufller chamber is provided within the housing with an ignition means mounted therein and an outlet therefrom disposed remotely from the ignition means. A bank of venturi pumps is disposed within the housing in the path of flow of exhaust gases entering said housing from the internal combustion engine. Each of the venturi pumps includes an inlet, throat and diffuser sections. The inlet section of each pump opens to the exhaust gases entering the housing, the throat section is provided with at least one port for receiving an additive gas comprising air and the diffuser section of each pump is open to the enclosed burner and mufiier chamber. Means are provided for supplying gas comprising air to each of the ports, the air being entrained into the individual venturi pumps by the pressure difference therebetween created by the flow of the exhaust gases through the venturi pumps. Means responsive to the operating conditions of the internal combustion engine are provided for bypassing a portion of the exhaust gases entering the housing past the bank of venturi pumps to .avoid the addition of gases comprising air within the bank to such bypassed gases. However, rather than emitting such bypassed exhaust gases to the atmosphere as in our copending application, they are directed into the burner and muffler chamber immediately after bypassing the bank of venturi pumps. All exhaust gases are passed through the burner and muffier chamber but the volume of air admixed with the exhaust gases under all conditions of load, power and speed is not over twice the volume of air added under idling conditions. Also, it is a particular feature of the present invention that silencing or muflling of all the exhaust gases passing into the burner and muffier chamber is accomplished by dividing each pressure pulse of exhaust gas entering the housing into individual elements and directing them through heat exchanger conduits of unequal length to attenuate or space the individual elements and thereby muffie the sounds of internal combustion.

The method of treating exhaust gases emitted from an internal combustion engine to complete the combustion thereof, according to the present invention, in general comprises the steps of: first establishing a primary flow path for pulses of exhaust gases emitted from an internal combustion engine. Each pulse of exhaust gases flowing in the primary path is then divided into a plurality of individual elements. An additive gas comprising air is introduced to each of the elements and mixed therewith to provide a plurality of individual mixtures comprising "an element of a pressure pulse of exhaust gas and an additive gas comprising air. Each mixture is then directed into a common chamber wherein combustion thereof may be elfected by spark ignition. A secondary flow path for at least a portion of the pulses of exhaust gases emitted from said internal combustion engine is selectively established in response to the operating conditions of the internal combustion engine. Upon operating conditions of the internal combustion engine causing increase in the flow rate of exhaust gases emitted therefrom, the secondary flow path is selectively placed in operation. The pressure pulses of exhaust gas following the secondary path are also divided into a plurality of individual elements and directed through conduits of unequal length into the burner chamber. The gases thus directed into the burner chamber from the primary and the secondary flow paths may then be ignited within the chamber by spark ignition and thereafter be emitted therefrom to atmosphere.

The foregoing and various other objects, uses and advantages of the present invention, as well as a better understanding thereof, will become apparent to those skilled in the art from a consideration of the following detailed description of exemplary embodiments of the afterburner and muffler device in accordance with the present invention. Reference Will be made to the appended sheets of drawings in which:

FIG. 1 is a diagrammatic side view of an internal combustion engine and its exhaust system equipped with an exemplary form of the afterburner and mufi ler device of the present invention;

FIG. 2 is an end view of the exemplary embodiment of afterburner and mufiler device of FIG. 1 taken therein along the plane IIII;

FIG. 3 is a longitudinal section view taken through the exemplary embodiment of afterburner and muffler device of FIG. 1 along the plane III-III therein;

FIG. 4 is a detail view of a portion of the device of FIG. 3;

FIG. 5 is a detail view of a portion of the exemplary embodiment of afterburner and muffler device of FIGS. 1-4;

FIG. 6 is a side view of an alternative exemplary embodiment of an afterburner and mufiier device in accordance with the present invention;

FIG. 7 is a longitudinal sectional view of the alternative exemplary embodiment of afterburner and mufiler device of FIG. 6 taken therein along the plane VII-VII;

FIG. 8 is a detail view of a portion of the alternative exemplary embodiment of afterburner and muffler device of FIGS. 6 and 7; and

FIG. 9 is a transverse section of the alternative exemplary embodiment of afterburner and mufller device of FIG. 7 taken therein along the plane IXD The ease with which the afterburner and mufller device of the present invention may be installed in a conventional internal combustion engine-exhaust system is exemplified by FIG. 1. Asshown there, the internal combustion engine 1 is provided with the usual exhaust manifold 2 having an exhaust outlet 3. As shown in our copending application Serial No. 195,789 filed May 18, 1962, such exhaust outlet 3 is ordinarily connected by means of an exhaust pipe with conventional form of mufiler. However, the device of the present invention, indicated generally by the numeral 10, may be associated with the exhaust outlet 3 replacing and obviating the conventional form of mufiier. The installation of the present device may be accomplished by any mechanic by the use of suitable adapters, variations in diameter of exhaust pipe, etc. being readily compensated for.

As shown in FIGS. 1 through 3, the preferred exemplary form of afterburner and mutlier device, indicated generally at 10, may be provided with a metal, insulated housing formed by upper and lower housing shells 11 and 12 respectively, shown bolted together in FIGS. 1 and 2 and with the upper shell removed in FIG. 3. Insulation material 13 may be provided within the housing to reduce the passage of heat and noise through the walls of the housing. The housing may be associated easily with exhaust pipe 3, leading from the internal combustion engine 1, by means of the housing inlet 14. Outlet 3 and housing inlet 14 may be fastened together by any suitable means, as for example, by the provision of the flanges 4 and 15 connected by bolts 16.

An enclosed burner and mufiier chamber is provided within the housing including an ignition means and an outlet therefrom. In the exemplary embodiment of FIGS. 1 through 5, the enclosed burner and mufiler chamber is preferably formed by an enclosure having at least one side wall 22 and opposing first and second end Walls, 21 and 23 respectively. Ignition means, indicated generally at 24 in FIGS. 1 and 5, are mounted in the afterburner and mufiler chamber on an end wall, preferably the second or far end wall 23 relative to the bank of venturi pumps, indicated generally at 30. Such ignition means 24 may comprise of a conventional spark plug. A metal shield 25 may be provided to prevent damage oc curring to the ignition means 24 from flying debris or other foreign matter when the device is employed under a moving vehicle. An outlet, indicated generally at 41 is provided from the afterburner and muffler chamber 20 through the side wall 22 for emitting exhaust gases from the chamber into the exhaust pipe 40 and from there to the atmosphere. Outlet 41 is preferably positioned adjacent the first end wall 21, near the bank of venturi pumps, indicated generally at 30, remote from the ignition means 24 so that the exhaust gases must pass forwardly through the chamber. Bafiles 42, 43, 44 and 45 may be provided to cause flow of exhaust gases from the end of afterburner chamber 20 near the ignition means 24 and second end wall 23 to flow in a serpentine manner to the outlet 41 near the first end wall 21 and remote from wall 23 and ignition means 24.

A bank of venturi pumps is provided Within the housing to receive exhaust gas from an internal combustion engine, admix an additional gas such as air and difiuse the mixture into the afterburner and muffler chamber 20. Each of said pumps is provided with an inlet section opening to exhaust gases entering the housing, a diffuser section opening to the enclosed burner and mufiier chamber through a heat exchanger tube and a throat section having at least one port therein. As shown in the exemplary embodiment of FIGS. 3 and 4, the throat sections 32 and diflifuser sections 33 are in a generally axially parallel array with each diffuser section positioned to discharge into the afterburner and rnufiier chamber 20 through the heat exchanger conduits indicated generally at 70. Inlet sections 34 opening to the exhaust gases entering the housing are provided in the exemplary embodiment by a fixed orifice plate 35 spaced forwardly in said housing from the end wall 21 of the afterburner and muffler chamber. Inlet sections 34, provided by the orifices in plate 35, are each aligned with a throat section 32 for directing elements of a pressure pulse of exhaust gas through the throat and diffuser sections into the afterburner and mufiler chamber 20. The effective throat zone of each venturi pump is provided between the venturi pump inlet 34 and the throat section 32 where the flow of exhaust gas through the pump passes through the space between plate 35 and wall 61. The cross section of the stream or jet of exhaust gas passing through such space expands slightly from the inlet sections or orifices '34 to the throat section 32, it smallest cross section existing, therefore, adjacent the wall or plate 35. The orifices or inlets 34 are preferably provided with a ratio of perimeter to cross-sectional area of about 20 inches per square inch to provide a similar ratio for thesmallest cross section of the exhaust gas flowing through the throat section of the pump. As described, uch smallest cross section occurs in the effective throat zone adjacent the plate 35.

Exhaust gas supply means, indicated generally at 50, in the exemplary embodiment may include the tubular inlet 14 adapted to be connected to the internal combustion engine exhaust outlet or pipe 3 and a housing 51 provided to direct exhaust gases to the fixed orifice means, plate 35 in the exemplary embodiment, and the inlet sections 34 of the bank of venturi pumps.

Means for supplying gas comprising air to the ports in the throat sections of the venturi pumps are provided in the exemplary embodiment as indicated generally at 60. Such means may include a housing formed by the fixed orifice plate or wall 35 and the spaced Wall 61. An additive gas, such as air and/or crankcase vent gases, may be introduced into the space between orifice plate 35 and wall 61 by an inlet conduit 62, such additive gas being drawn through a filter 63 against a deflection plate 64. Means are provided in association with the inlet sections, throat sections 32 and wall 61 for providing at least one port for each throat section Opening between said fixed orifice plate 35 and wall 61 outwardly of the afterburner and mufiler chamber 20. Such port may be considered to be formed around the gas stream or jet of exhaust gas passing from the inlets 34 to the throat sections 32 by the spacing of plate means 35 from the wall 61 and the lip means 36 on the throat section 32. The port thus formed may be considered to provide a bandlike opening around each exhaust gas stream or jet exposing the perimeter of such gas jet to the additive gas comprising air introduced between the plate 35 and wall 61. The additive gas is supplied in a single body thereof directly to and completely around the perimeter of each of the ports in the throat sections 32 without preheating and in variable amounts further controllable by the setting of closure means 65 on the inlet conduit 62.

A plurality of heat exchanger conduits for directing exhaust gas fiow into the afterburner and mufi'ler chamber toward the ignition means in heat exchange relation to the interior of such chamber is provided. In the exemplary embodiment, such heat exchanger conduits are indicated generally at 70. Each conduit 71 is of a generally tubular configuration with an inlet portion 72 mounted in the first end wall 21 of the afterburner and mufller chamher and an outlet portion 73 opening toward said end wall 23 and ignition means 24. Each of the heat exchanger conduits is provided with a larger cross section at its outlet portion'within the chamber 20 than at its inlet section adjacent the wall 21, the inlet section be of generally frusto-conic configuration, so that the flow of exhaust gases through the conduits is promoted by a reduction in pressure experienced by gas flowing through the conduits. As shown in FIG. 4, each of said heat exchanger tubes 71 is disposed within the chamber 20 with its inlet portion mounted in the end wall 21 and surrounding an outlet portion of a diffuser section 33. The mounting means 74 for each inlet section 72 of the heat exchanger conduits 71 for mounting the inlet section 72 in the end wall 21 defines an annular port, indicated at 75, opening to the afterburner and mufller chamber 20 through the interior of the heat exchanger tube 71.

Means responsive to the operating conditions of the internal combustion engine 1 for bypassing a portion of the exhaust gases past the bank of venturi pumps, indicated generally at 30, to the inlet portions of heat exchanger tubes or conduits, indicated generally at 70, are provided so that all exhaust gases pass through the heat exchanger tubes or conduits and the amount of air admixed into the total volume of exhaust gases by said blank of venturi pumps, indicated generally at 30, is not substantially increased when the flow rate of exhaust gases into said housing is increased more than twice the minimum flow rate of exhaust gases. As shown in the exemplary embodiment of FIGS. 3 and 4, such means indicated generally at 80, may comprise a valve housing 81, a valve housing inlet conduit 82, a valve 83 and an outlet 84 opening said valve housing to a space 90 formed between the wall 61, of the exemplary means for supplying gas comprising air to the ports in the throat sections of the venturi pumps, and the first end wall 21 of the afterburner and muffler chamber 20. The valve 83 may be pivotally mounted by an arm 85 on a pivot axis 86 so that it may seat upon or abut a seat or limit stop 87 formed by the inlet 82. An actuator 88 acts through a link 89 and arm 91 connected to the pivotal axis 85 of valve 83 to move the valve between open and closed positions. Actuator 88 includes a spring-biased diaphragm with the link 89 connected to a central area thereof. One side of the diaphragm is open to atmospheric pressure while the opposite side of the diaphragm is interconnected to the intake manifold of the engine by an enclosed tube 92. The pressure within the intake manifold is always somewhat lower than atmospheric pressure, varying from a fraction of a pound per square inch less than atmospheric pressure when the throttle is wide open, to as much as twelve pounds per square inch less than atmospheric when the throttle is fully closed during deceleration conditions or when the engine is being used for braking action, as when a vehicle goes down hill with the throttle closed and clutch engaged. The spring bias in the actuator opposes the diaphragm movement caused by the intake manifold suction pressure and biases the valve 83 into an open position. In normal operation, after the engine has been started and the car is idling, the suction in the intake manifold is about nine to ten pounds per square inch. The actuator is designed to allow movement of the diaphragm against the resistance of the aforementioned spring means to close the modulating valve 83 and thus directing all of the exhaust gases through the inlet sections or orifices 34 in the bank of venturi pumps indicated generally at 30. The closed position of valve 83 shown in FIG. 3 is typical of the positioning of valve 83 during deceleration or idling conditions of the internal combustion engine and is the condition for minimum exhaust gas flow. Also the maximum proportion of added air is then required. When the engine throttle is opened to increase engine power to cause movement of the car, the suction in the intake manifold changes to between seven to five pounds per square inch suction which is not sufficient to keep the actuator spring fully compressed, particularly with the additional eifect of increased exhaust gas pressure on the modulating valve 83, as exhaust gases enter the exhaust gas supply means indicated generally at 50. The valve means is preferably adjusted to cuse initial opening of the valve as the intake manifold suction changes from about eight pounds per square inch to a value of about five pounds per square inch when the valve is fully open. The valve means is thus responsive to increased absolute engine intake manifold pressure and to the increase in flow of exhaust gas from the engine 1. Upon acceleration of the engine 1, the valve means bypasses a portion of the exhaust gases past the bank of venturi pumps, indicated generally at 36 into the space, indicated generally at 90, formed between walls 61 and 21 and from there, through the heat exchanger conduits, indicated generally at 70, into the afterburner and mufiler chamber 20. By controlling the proportion of exhaust gases directed around the bank of venturi pumps to the chamber 90 in response to the operating conditions of the internal combustion engine, as indicated above, the volume of air admixed with exhaust gases under idling conditions may be maintained about 40% of the volume of exhaust gases supplied to the bank of venturi pumps and the volume of air admixed under all other conditions of load, power and speed not over twice the volume of air added under idling conditions.

Walls 61 and 21 of the exemplary embodiment of FIGS. 1 through 5 along with an outer enclosure wall 93 define chamber 90 about the diffuser sections 33 of the venturi pumps. Means are associated with such walls, particularly the conduit mounting means 74, defining annular ports indicated generally at opening to each heat exchanger tube 71 from the chamber or space 90. Therefore, exhaust gas bypassed by the valve means, indicated generally at 80, about the bank of venturi pumps, indicated generally at 30, is directed through valve housing outlet 84 into the chamber about the diffuser sections 33 and through the individual annular ports, indicated generally at 75, and into the heat exchanger conduits or tubes, indicated generally at 70, to the afterburner and muffler chamber 20. Such bypassed exhaust gases are mixed within the heat exchanger tubes or conduits along with the mixtures of exhaust gas and additive gas emitted by the bank of venturi pumps into the heat exchanger tubes or conduits. All exhaust gases and added gases are thus directed into the afterburner and muffler chamber 20 through the heat exchanger tubes or conduits. It is a particular feature of the present invention that the heat exchanger tubes or conduits, indicated generally at 70, are provided in unequal lengths so that a pulse of exhaust gas emitted from the internal combustion engine directed into and divided among the heat exchanger tubes or conduits is emitted into the afterburner and mufller chamber 20 as separate elements in spaced intervals. Each pressure pulse of exhaust gas may thereby be attenuated and the noise of internal combustion etfectively silenced within the device.

Combustion of the exhaust gases within the afterburner and muffler chamber 20 may be effected by spark ignition 9 by the ignition means 24. The ignited gases pass back through the chamber 20 about the heat exchanger tubes or conduits in serpentine fashion, and in heat exchange relation thereto, to the outlet 41 of exhaust pipe 40 to emit such attenuated and mufl'led exhaust gases to the atmosphere.

An alternative exemplary embodiment of the afterburner and mufller device of the present invention is shown in FIGS. 6 through 9. Referring first to FIG. 6, it can be seen that the alternative exemplary embodiment of the afterburner and mufiier device, indicated generally at 100, may be provided with a metal, insulated housing formed by upper and lower housing shells 111 and 112 respectively. The housing shells may be both fitted together, welded or fastened together by any suitable means. As shown in FIG. 7, insulation material 113 may be provided within the housing to reduce the passage of heat and noise through the Walls thereof. The housing may be associated easily with an exhaust pipe 3 by means of a housing inlet 114 shown fitted Within the pipe 3. Inlet 114 may be securely fastened within the exhaust pipe 3 by welding or any other suitable fastening means.

An enclosed burner and mufller chamber is provided within the housing in the alternative exemplary embodiment as indicated at 120. Enclosed burner and mufiler chamber 120 is preferably formed by an enclosure having at least one side wall 122 and opposing first and second end walls 121 and 123 respectively. Ignition means, indicated generally at 124, may be mounted in the afterburner and mufiler chamber on end wall 123 preferably remote from the bank of venturi pumps, indicated generally at 130, and the outlet from chamber 120 to be subsequently described. As shown in FIG. 6, metal shield means, indicated at 125, may be provided to protect the ignition means from flying debris or other foreign matter which the device might encounter when employed under a moving vehicle.

In the present alternative exemplary embodiment of FIGS. 6 through 9, the outlet means of the afterburner and mufiler chamber 120 is provided by a ported exhaust pipe or outlet, indicated generally at 140. Such exhaust outlet or pipe from the afterburner and mufiler chamber is provided with large ports 141 near the first end wall 121 of the chamber remote from the ignition means 124 so that the exhaust gases in leaving the chamber, indicated generally at 120, must pass forwardly through the chamber back past the plurality of heat exchanger tubes or conduits indicated generally at 170. Additional, smaller ports 142 and 143 are provided in the exhaust pipe or outlet of, the alternative exemplary embodiment to allow the partial discharge of exhaust gases flowing forwardly Within the afterburner and muffler chamber toward the large outlet ports 141. As in the prior embodiment, bafiles 144 and 145 may be provided within the afterburner and muflier chamber about the heat exchange tubes or conduits to cause exhaust gases passing forwardly within the afterburner and mufl'ler chamber toward the outlets 141 to flow in a serpentine manner, ensuring flow of such exhaust gases about each heat exchanger tube or conduit.

A bank of venturi pumps is provided within the housing 110 to receive exhaust gas from an internal combustion engine, admix an additional gas such as air and diffuse the mixture into the afterburner and mufller chamber 120 as in the prior embodiment. Such means are indicated generally at 130 and include a fixed orifice plate 135 providing inlet sections 134, throat sections 132 and diffuser sections 133 mounted in a generally axially parallel array on wall 161. Each diffuser section 133 is positioned to discharge into the afterburner and muffler chamber through the heat exchanger conduits 171. Round edge orifices are preferred.

Exhaust gas supply means in the alternative exemplary embodiment indicated generally at 150 and include the tubular inlet 114 adapted to be connected to the internal combustion engine exhaust outlet or pipe 3 and a housing 151 provided to direct inflowing exhaust gases to the plate and its inlet section 134.

Means for supplying gas comprising air to and completely around the perimeter of the ports in the throat sections of the venturi pumps are provided, as indicated generally at 160. Such means in the alternative exemplary embodiment include a housing formed by the fixed orifice plate or wall 135 and a spaced wall 161. AS in the prior embodiment, an additive gas, such as air and/or crankcase vent gases, may be introduced into the space between the orifice plate 135 and wall 161 by an inlet conduit 162. The gas comprising air drawn into the inlet 162 into the space between the orifice plate 135 and wall means 161 provides a single body of gas comprising air surrounding the perimeters of the ports 136 of the venturi pump throat sections. Exhaust gases directed through the plurality of inlet sections provided by the orifice plate 135 flow in jets of exhaust gases through this body of added gases comprising air. As previously described with the prior embodiment, the additive gas comprising air is entrained into the jets of exhaust gas flowing through the individual venturi pumps formed by the inlet sections 134, throat sections 132 and diffuser sections 133.

A plurality of heat exchanger tubes or conduits for directing exhaust gas flow into the afterburner and mufller chamber toward the ignition means in heat exchange relation to the interior of such chamber is provided in the alternative exemplary embodiment, as indicated generally at 170. Each conduit 171 is of generally tubular configuration of constant cross section for its entire length with an inlet portion 172 mounted in the first end wall 121 of the afterburner and mufller chamber and an outlet portion 173 opening toward the end Wall 123 and ignition means 125. As shown in FIG. 8, the mounting means 174 for each inlet section 172 is comprised by deforming the inlet section to grasp the end Wall 121 when inserted therein. Such mounting means 174 for each inlet section defines an annular port, indicated at 175, opening to the afterburner and mufller chamber 120 through the interior of the heat exchanger tubes 171.

Means responsive to the operating conditions of the internal combustion engine 1 for by-passing a portion of the exhaust gases past the bank of venturi pumps to the inlet portions of the heat exchangers tubes or conduits are provided so that all exhaust gases pass through the heat exchanger tubes or conduits into the afterburner and muffler chamber in the alternative exemplary embodiment. Such means as shown generally at 180, comprise a valve housing 181, a valve housing inlet 182, and a valve 183. Valve housing 181 in the present alternative exemplary embodiment is formed in part by the wall means 161 and end wall 121 of the afterburner and muflier chamber. The valve 183 may be pivotally mounted and operated in response to changes and operating conditions of an internal combustion engine as described in detail with relation to the prior preferred exemplary embodiment.

Walls 161 and 121 of the alternative exemplary embodiment along with additional outer enclosure Walls 193 define a chamber about the diffuser sections 133 of the venturi pumps. The conduit means 174 provide annular ports, indicated generally at 175, opening the chamber 190 to the heat exchanger tubes 171. Therefore, exhaust gases by-pass about the bank of venturi pumps by the valve means indicated generally at 130, are directed through the valve housing into the chamber 190 through the heat exchanger conduits or tubes, indicated generally at 170, and to the afterburner and the mufiler chamber 120. As in the prior embodiment then, all exhaust gases and added gases are directed into the afterburner and muffler chamber 120 through the heat exchanger tubes or conduits.

It is a particular feature of the present alternative exemplary embodiment that the heat exchanger conduits 171 are of unequal length to discharge exhaust gases into the chamber 120 toward the ignition means 124 in attenuated, spaced relation. The exhaust gases are then redirected about the exterior of the heat exchanger conduits past the plurality of outlet ports 143, 142 and 141 to be emitted to atmosphere through the exhaust or outlet pipe, indicated generally at 140. Additional silencing or mufiiing of the alternative exemplary embodiment is obtained by allowing partial dispersion of exhaust gases through the smaller outlet ports 142 and 14-3 prior to the main flow of exhaust gases through the larger outlet ports 141.

The method of treating exhaust gases emitted from an internal combustion engine to complete the combustion thereof has been partially disclosed herein by the prior detailed descriptions of exemplary embodiments of apparatus, according to the present invention, which employ the method. The first step in the present method is to establish a primary fiow path for pulses of exhaust gases emitted from an internal combustion engine. The exhaust gas flowing in the primary path is then divided into a plurality of individual and distinct generally circular, parallel gas jets, each pressure pulse thereof being divided into individual elements.

The exhaust gas jets are then directed through a single body of additive gas comprising air to entrain amounts of such additive gas with each gas jet. In the exemplary embodiments described herein, such gas jets are formed by passing the exhaust gases through the multi-orificed plates 35 and 135. The jets so formed are then directed through the body of additive gas disposed within the chamber 90 and 199 formed between the respective orifice plates 35, 135 and the wall means 61 and 161. Mixing of the entrained additive gases with the jets of exhaust gases is then accomplished by directing such jets into the throat and diffuser sections of the bank of venturi pumps. Each mixture is thereafter separately passed into the afterburner and mufiler chamber through the heat exchanger conduits or tubes. The mixtures may then be subjected to combustion within such chamber common to all the mixtures.

Further, in accordance with the present method, a secondary flow path for at least a portion of the pulses of exhaust gases emitted from the internal combustion engine is selectively established in response to the operating conditions of the internal combustion engine. Upon an increase in absolute pressure in the intake manifold and the increase in flow of exhaust gas from the internal combustion engine, a secondary fiow path for a portion of the pulses of exhaust gases is established to direct such portions into the aforementioned common chamber without the steps of introducing an additive gas comprising air and the mixing of the exhaust gas elements and additive gases occurring in the primary flow path. Upon establishing the secondary flow path in response to the operating conditions of the internal combustion engine by opening the valve means in the exemplary embodiment, the portions of pulses of exhaust gases following the secondary flow path are directed into the common chamber with the exhaust gases and additive gases flowing in the primary flow path. All gases in the chamber are then subjected to combustion by igniting them and are thereafter emitted to atmosphere. According to the present method, therefore, while all exhaust gases from the internal combustion engine are passed into the common chamber where the step of combustion occurs, only the exhaust gases following the primary flow path are subjected to the steps of adding and mixing an additive gas comprising air.

It is a further feature of the present method that all exhaust gases following both the primary fiow path and secondary fiow path may be divided into a multitude of individual pressure pulse elements. The exhaust gases following the primary fiow path may be divided in passing through the bank of venturi pumps and then directed in such divided state through the heat exchanger conduits or tubes, indicated generally at 70, in the exemplary embodiment of FIGS. 1 through 5. The flow of exhaust gases through the secondary path may also be divided into a multitude of individual pressure pulse elements. In the exemplary embodiment of FIGS. 1 through 5, for example, it can be seen that the flows of exhaust gases past the valve 83, through chamber 90 and into the plurality of heat exchanger conduits or tubes, indicated generally at 70, and also that through the annular ports are effectively divided into a multitude of individual pressure pulse elements. The flow of divided pressure pulse elements in both the primary flow path and secondary flow path are commingled within the heat exchanger conduits or tubes prior to their introduction into the common chamber, as chamber 20 within the exemplary embodiment of FIGS. 1 through 5. The heat of all the exhaust gases is thus presented to the afterburner and muffier chamber during initial warm-up of the engine with the throttle open above that required merely for engine idling.

A study of exhaust velocity through exhaust pipes with relation to the number of cylinders firing has shown average exhaust gas pulse spacing of from 27 inches to 38 inches. The over-all average spacing has been found to be about 30 inches between primary pulses regardless of engine displacement. There is a variation in this spacing between specific pulses on a single engine because of the engine firing order and exhaust system dimensions, i.e. six cylinder or eight cylinder and V-type or siamesed exhaust pipes. To prevent the overlapping of the efiect of succeeding pressure pulses when attenuating them according to the present method, it has been found expedient to spread each pulse out over a length of 16 to 24 inches. For example, in the method employed by the alternative exemplary embodiment herein, when the valve means is open under powered operation of the internal combustion engine, the exhaust gas has to travel unequal distances from the valve opening to enter the respective rows of heat exchanger tubes, whether pasing through the bank of venturi pumps or by-passing such bank and entering through the chamber 190. Thus, individual or distinct elements of each pressure pulse enter the nearest tube first so that by the time the pulse has reached the second row of tubes, from the bottom in FIG. 7, the element or partial pulse in the first row of tubes has travelled a distance down the first tube equal to approximately the distance between the first (bottom) row of tubes and the second row. This movement and division of each pressure pulse of exhaust gas continues proportionately with relation to the remaining rows of tubes as well. When the partial pressure pulse or element emitted from each of the heat exchanger conduits or tubes of the first (bottom in FIG. 7) row of tubes, the partial pulse or element in each of the second row of tubes is approximately two inches behind each of the elements in the first tubes. The provision of unequal length flow paths by the heat exchanger tubes for each row of elements causes a further attenuation or spacing of the elements in the first and second rows. Thus when each element or portion of an exhaust gas pulse is exiting from a heat exchanger tube in the second row, each element or portion of exhaust gas pulse emitted from the first row of heat exchanger tubes is already returning forwardly within the chamber toward the exhaust ports 141 providing as much as three inches gap between the elements in the first and second rows of partial pulses or elements. A similar circumstance occurs between the successive rows of heat exchanger tubes or conduits so that an original single pressure pulse of exhaust gas may be divided not only into a plurality of individual elements, but be spread over a distance, in the exemplary embodiment of FIG. 7, for example, of somewhat better than 10 inches. This spread can be controlled by adjusting the relative lengths of the heat exchanger conduits to increase or decrease such spread.

In the exemplary embodiment of FIG. 7, additional spread of the presure pulse elements may be effected by providing release holes in the end of the second bafiie 144 near the exhaust-tube, indicated generally at 140, providing a short path for exhaust gas directed toward ports 141 as well as the long path around battle 144. Such provision may further spread the original pulse an additional six inches or more making the total pressure pulse spread in the exemplary embodiment of FIG. 7 at least 16 inches. As indicated previously, it is desirable that such spread of each exhaust gas pulse be over a length of about 16 to 24 inches. When the present device is used with internal combustion engines of small cubic displacement such as 8 cubic inches displacement or less, there may be only a limited number of venturi pumps employed in the bank and a corresponding number of heat exchanger tubes available for spreading the exhaust gas pulse. In such case, additional partial pressure release openings may be provided in selected tubes or conduits of the heat exchanger conduit means indicated generally at 170 so as to allow release of portions of the pulse prior to emission from the ends of such heat exchanger tubes and cause the spreading of the original pulse over as much as a distance of twenty inches. However, the method and apparatus as disclosed in the prior exemplary embodiments is pre ferred.

It has been found that under all normal operating conditions, the temperatures within the afterburner and muffier chamber of the present device are maintained in a range between a minimum of about 800 to 1,000 F. and a maximum of 1800 to 1900 F. Internal combustion engines with fouled sparkplugs or that are poorly maintained can emit abnormally high portions of combustibles into the exhaust and abnormally high combustion chamber temperatures may result. It has also been found that on long mountainous downgrades where the engine is used as a braking-aid, the combustion chamber temperatures resulting from such steady state deceleration can continue to climb to particularly abnormally high temperatures. Also, in view of the heat exchanger means provided within the afterburner and mufller chamber, rising temperatures in such chamber cause increasing temperatures of the incoming gases and therefore a compounding in the rise in combustion temperatures within the chamber may occur. As safety protection for the present device, a thermal sensor of generally known construction has been employed within the chamber and associated with the means responsive to the operating conditions of the internal combustion engine for by -pass ing a portion of the exhaust gases past the bank of venturi pumps. The thermal sensor may be adjusted to be operated by abnormally high combustion temperatures, but below a destruction temperature, to cause operation of the exhaust modulating valve by-passing a portion of the exhaust gases past the gas comprising air pumping section or venturi pumps. This will cause a reduction in the proportion of gas comprising air being pumped into the exhaust gases entering the afterburner and muffler chamber and therefore reduce the amount of combustion taking place therein. A lowering of combustion temperatures during these abnormal conditions may therefore be efl ected to prevent the destruction of the device by the otherwise resultant abnormally high combustion temperatures. In the exemplary embodiments disclosed herein, such conventional thermal sensor employed wtih the aforementioned means for bypassing exhaust gases has been adjusted to maintain a top combustion temperature of 2100 to 2200 F.

From the foregoing descripton of exemplary embodiments of the methods and apparatus of the present invention, it can be seen that the afterburner and mufiier chamber of the present device may be readily associated with the exhaust outlet or pipe of any internal combustion engine. The device modifies the exhaust gas from such engine to complete the combustion therein, attains stabilized burning within the burner chamber more quickly than was heretofore possible, sustains combustion within the inner chamber during deceleration of the internal combustion engine within shorter periods after starting of the engine and effectively treats and mufiies the sounds of internal combustion emitted from the internal combustion engine prior to the emission of such exhaust gases to atmosphere. The device may be readily attached not only to new internal combustion engines and vehicles employing them, but is adapted to be readily attached to existing vehicles by merely replacing existing mufiiers with a device of the present invention. The present device further provides a long trouble-free life of operation, is easy to manufacture, does not employ catalysts which must be periodically replaced, and will continue to operate effectively continuous in all situations of use even where the internal combustion engine may be poorly maintained, abused or gradually ages. The present device and the ethod it employs allows the burning of exhaust gases with air added in approximate accordance with the variation in the hydrocarbon content of the gases under diflerent operating conditions of the engine, while automatically and without the use of complicated or expensive machinery or additional mufflers, effectively muflling or silencing all exhaust gas emitted from the internal commustion engine. Such mufiiing or silencing is accomplished by the present method and the apparatus employing such method, as disclosed herein, by directing pressure pulses of exhaust gases in predetermined flow paths for introducing an additive gas comprising air to a portion of the pulses and mixing such portions and additive gas while etfectively dividing all exhaust gas pulses into a plurality of individual or distinct elements and thereafter eifectively attenuating or spacing such elements as they are emitted into the afterburner and muffler chamber by the herein disclosed heat exchanger means.

Having thus disclosed exemplary embodiments of apparatus and methods of the afterburner and muffier device of the present invention, we wish it understood that various modifications, alterations and adaptations of the afterburner and mufiler device as disclosed herein may come within the scope of the invention which is defined by the following claims.

We claim:

1. An afterburner and muflier device for use in modifying exhaust gases from an internal combustion engine, comprising:

a housing to be associated with an exhaust pipe of an internal combustion engine;

an enclosed burner and mufiler chamber in said housing including an ignition means and an outlet therefrom;

a plurality of heat exchanger conduits within said enclosed burner and mufiler chamber having inlet portrons mounted in and opening through an end wall of Said chamber, the outlet portions of Said conduits opening within said chamber toward said ignition means;

a bank of venturi pumps within said housing, each of said pumps having an inlet section opening to exhaust gases entering said housing, a diffuser section opening to the enclosed burner and mufller chamber through said heat exchanger tubes and a throat section having at least one port therein;

means for supplying gas comprising air to the ports in the throat sections of said venturi pumps;

means for communicating the inlet portions of said heat exchanger tubes past said bank of venturi pumps to the exhaust gases entering said housing; and

means responsive to the operating conditions of said internal combustion engine for bypassing a portion of said exhaust gases past said bank of venturi pumps to the inlet portions of said heat exchanger tubes through said communicating means so that all exhaust gases from said internal combustion engine pass through said tubes and combustion chamber but the amount of air admixed into the total volume of exhaust gases by said bank of venturi pumps is not substantially increased when the flow rate of exhaust gases into said housing is increased more than twice the minimum flow rate of exhaust gases.

2. An afterburner and mufiler device as in claim 1 wherein the heat exchanger tubes are of unequal length to disperse exhaust gas pressure pulses entering said burner chamber.

3. An afterburner and muffler device as in claim 1 wherein the inlet portion of each heat exchanger tube has a smaller diameter than the remainder of the tube so that a reduction in pressure is effected within the tubes as the exhaust gases pass therethrough.

4. A combination afterburner and muffler device for use with the exhaust pipe of an internal combustion engine for modifying exhaust gases therefrom, comprising:

an enclosed burner and muffler chamber having an inlet, an outlet and an ignition means mounted therein;

a plurality of heat exchanger conduits for directing exhaust gas flow into said chamber toward said ignition means in heat exchange relation to the interior of said chamber;

first means for supplying exhaust gases to said heat exchanger conduits including means for admixing gas comprising air into said exhaust gases in proportion to the flow rate of said exhaust gases through said first means;

second means for supplying exhaust gases without admixing ga comprising air to said heat exchanger conduits bypassing said first means; and

means responsive to the operating conditions of said internal combustion engine for selectively directing exhaust gases to said first and second means for supplying exhaust gases to said heat exchanger conduits so that all exhaust gases pass through said heat exchanger conduits but the amount of gas comprising air admixed to the exhaust gases passing through said conduits is not substantially increased when the flow rate of exhaust gases into said device is increased more than twice the minimum fiow rate when said engine is idling.

5. The combination afterburner and muflier device of claim 4 wherein said first means for supplying exhaust gases to said heat exchange conduits comprises a bank of venturi pumps, each of said pumps including an inlet section opening to said exhaust gases, a diffuser section opening to said heat exchange conduits and a throat section having at least one port therein opening to said means for admixing gas comprising air into said exhaust gases; and

wherein said second means for supplying exhaust gases to said heat exchange conduits bypassing said first means includes wall means defining a chamber about the diffuser sections of said venturi pumps and means associated with said wall means defining a port to each said heat exchanger tube.

6. The method of treating exhaust gases emitted from an internal combustion engine to complete the combustion thereof comprising the steps of:

establishing a primary flow path for pulses of exhaust gases emitted from an internal combustion engine;

dividing each exhaust gas pressure pulse flowing in said primary path into several distinct generally circular parallel jets;

directing said jets through a single body of additive gas comprising air to entrain an amount of said additive gas with each of said jets;

passing each said distinct jet and an amount of entrained additive gas through a ditfuser to mix said jet and entrained gas separately from each other distinct jet;

directing each separate mixture of exhaust gas jet and entrained additive gas into a common chamber;

selectively establishing a secondary flow path for at least a portion of the pulses of exhaust gases emitted from said internal combustion engine in response to the operating conditions of said internal combustion engine;

dividing said portion of pulses of exhaust gases into a plurality of individual elements;

directing elements of pulses of exhaust gases following said secondary fiow path into the separate mixtures of exhaust gas and additive gas prior to their entry into said common chamber;

subjecting all said exhaust gases and said additive gases to combustion in said chamber; and

emitting said gases to atmosphere.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 12/49 France.

JULIUS E. WEST, Primary Examiner. 

4. A COMBUSTION AFTER BURNER AND MUFFLER DEVICE FOR USE WITH THE EXHAUST PIPE OF AN INTERNAL COMBUSTION ENGINE FOR MODIFYING EXHAUST GASES THEREFROM, COMPRISING: AN ENCLOSED BURNER AND MUFFLER CHAMBER HAVING AN INLET, AN OUTLET AND AN IGNITION MEANS MOUNTED THEREIN; A PLURALITY OF HEAT EXCHANGER CONDUITS FOR DIRECTING EXHAUST GAS FLOW INTO SAID CHAMBER TOWARD SAID IGNITION MEANS IN HEAT EXCHANGE RELATION TO THE INTERIOR OF SAID CHAMBER; FIRST MEANS FOR SUPPLYING EXHAUST GASES TO SAID HEAT EXCHANGER CONDUITS INCLUDING MEANS FOR ADMIXING GAS COMPRISING AIR INTO SAID EXHAUST GASES IN PROPORTION TO THE FLOW RATE OF SAID EXHAUST GASES THROUGH SAID FRIST MEANS; SECOND MEANS FOR SUPPLYING EXHAUST GASES WITHOUT ADMIXING GAS COMPRISING AIR TO SAID HEAT EXCHANGER CONDUITS BYPASSING SAID FIRST MEANS; AND MEANS RESPONSIVE TO THE OPERATING CONDITIONS OF SAID INTERNAL COMBUSTION ENGINE FOR SELECTIVELY DIRECTING EXHAUST GASES TO SAID FIRST AND SECOND MEANS FOR SUPPLYING EXHAUST GASES TO SAID HEAT EXCHANGER CONDUITS SO THAT ALL EXHAUST GASES PASS THROUGH SAID HEAT EXCHANGER CONDUITS BUT THE AMOUNT OF GAS COMPRISING AIR ADMIXED TO THE EXHAUST GASES PASSING THROUGH SAID CONDUITS IS NOT SUBSTANTIALLY INCREASED WHEN THE FLOW RATE OF EXHAUST GASES INTO SAID DEVICE IS INCREASED MORE THAN TWICE THE MINIMUM FLOW RATE WHEN SAID ENGINE IS IDLING. 